i would have to guess its because with out a larger/thicker atmosphere you could not hold the heat in.

no that's not it the heat would have to be given off as heat radiation (not the radioactive), because in space heat can only be transfered that way or by charged particles from the sun. After all space is the greatest insulator. If we were talking about normal situations that would be a fine explaination, but in this situation heat can't be transfered out by convection or the other kind of heat transfer that I just forgot the name too.

conduction is the other type of heat transfer.

Thanks, so how would the heat be lost though? Because another, more crazy idea was to nuke the planet to warm it up. My idea, except for the nuclear radiation, runs on the same principles, basically creating alot of heat to free the gas particles.

I recommend you read Mars series by Kim Stanley Robinson, starting with "Red Mars." In those books, the process for terraforming Mars is demonstrated, and to a certain extent, explained. As far as I could tell, it's all good science, even though it is a fictional account.

I thought the problem with Mars was it's core. You could generate heat and gases, but the solar winds would ultimately blow them away without the protection of a large magnetic core (such as ours). You would probably need a Buck Rogers or Spaceballs type force field surrounding the planet to keep the gases in. May the schwartz be with you.....

or we could use kogasu's nukes and follow the process discribed in the move Core : ). that should start the core spinning again creating the magnetic field. then create some green house gasses and we should have a livable planet in what 10 -15 years : ). because we all know things we see on tv and in movies are real.

Actually my idea was to use nuclear generators to create heat and then use microorganisms to make the atmosphere breathable. I don't like the idea of using nuclear warheads because then you'll have a planet with an atmosphere, but nobody could live there because of all the radiation.

I don't think it's possible to restart the core once it's a hunk of rock.

Theoretically if this were to happen how would we make something to deflect solar winds, because that alone would stop us from moving there.

The core is definately the biggest problem. I would have to imagine that livable conditions free from being cooked alive would have to wait until technology is able to make some sort of giant electromagnetic deflection system.